Breslow et al disclosed the polymerization of ethylene using a metallocene catalyst in U.S. Pat. No. 2,924,593.
The use of an aluminoxane as a cocatalyst for ethylene polymerization catalyst was reported by Manyik et al in U.S. Pat. No. 3,231,550.
Subsequently, Kamisky and Sinn discovered that aluminoxanes are excellent cocatalysts for metallocene catalysts, as disclosed in U.S. Pat. No. 4,404,344.
The use of a supported aluminoxane/metallocene catalyst is further described in, for example, U.S. Pat. No. 4,808,561 (Welborn et al, to Exxon).
Hlatky and Turner disclosed the activation of bis-cyclopentadienyl metallocene catalysts with boron activators in U.S. Pat. No. 5,198,401.
Boron activators and aluminoxane are expensive. Accordingly, a less expensive catalyst activator would be a useful addition to the art. We have now discovered a catalyst activator system comprising i) a solid zirconium acid component and ii) a hydrocarbyl aluminum.